Technical Abstract:
Glyphosate [N-(phosphonomethyl)glycine]-resistant crops (GRCs), canola (Brassica napus L.), cotton (Gossypium hirsutum L.) maize (Zea mays L.), and soybean [Glycine max (L.) Merr.], have been commercialized and grown extensively in the Western Hemisphere and, to a lesser extent, elsewhere. Glyphosate-resistant cotton and soybean have become dominant in those countries where they can be grown. Effects of glyphosate on contamination of soil, water, and air are minimal, compared to that caused by some of the herbicides that they replace. No risks have been found with food or feed safety or nutritional value in products from currently available GRCs. GRCs have promoted the adoption of reduced- or no-tillage agriculture in the USA and Argentina. Weed species in GRC fields have shifted to those that can more successfully withstand glyphosate or to those that avoid the time of its application. At least one weed species [Conyza Canadensis (L.) Cronq.] has evolved resistance to glyphosate in GRCs. GRCs have greater potential to become problems as volunteer crops than do conventional crops. Glyphosate resistance transgenes have been found in fields of canola that are supposed to be non-transgenic. Under some circumstances, transgene flow (introgression) from GRCs to related species that might become problems in natural ecosystems may be the largest risk of GRCs. Glyphosate resistance transgenes themselves are highly unlikely to be a risk in wild populations, but when linked to transgenes that may impart fitness benefits outside of agriculture (e.g., insect resistance), and natural ecosystems could be affected. The development and use of failsafe introgression barriers in crops with such linked genes is needed.